Pure substances melt at a precise temperature. Complex mixtures such as edible fats and oils have a temperature range over which melting occurs. It is common to measure the lowest temperature at which the mixture behaves as a liquid and designate that temperature as its melting point.
This invention has been made in the context of determining the melting point of materials such as animal fats. Animal fats are mixtures of long chain fatty acids largely in the form of triglycerides. The melting point of a particular fat is largely determined by the proportion of saturated, monounsaturated and polyunsaturated fatty acids (SFAs, MUFAs and PUFAs, respectively) and the carbon chain length. The greater the proportion of SFAs, the higher the melting point of the particular fat. The shorter the fatty acid chains, the lower the melting point.
The type of fat in the diet is as important as the quantity for maintaining good health. Diets that replace SFA with MUFA or PUFA are similar to or better than diets that replace SFA with carbohydrates. These effects can be seen in fasting glucose and cholesterol profile and on coronary heart disease. While there has been a substantial public health effort in many countries to reduce the proportion of SFAs in diets, this has been largely focused on processed foods and reduction in consumption of animal fats. Hitherto there has been little recognition of the substantial variations in the SFA component in meat within and between species and under different animal production systems. Furthermore, increased MUFA content has been linked to better taste and texture of meat. Interest is growing in improving the MUFA content of meat and other meats. The effect of MUFA and PUFA content on palatability and health is associated with their lower melting points (TM). Even within the SFA, lauric acid has a lower TM than stearic or palmitic acid and a better effect on the ratio of total cholesterol to high-density lipoprotein cholesterol.
Fat melting point is expected to have a growing role as a simple indicator of the fatty acid components and hence the health and palatability characteristics of meat.
Currently there are several methods for measuring the TM of fat, of which the most commonly used is the slip point or open capillary method (American Oil Chemists' Society official method Cc 3b-92; AOCS, 1998), the softening point (American Oil Chemists' Society official method Cc 3-25; AOCS, 1998), the point at which the fat becomes clear (American Oil Chemists' Society official method Cc 1-25; AOCS, 1998), the dropping point (American Oil Chemists' Society official method Cc 18-80; AOCS, 1998), and differential scanning calorimetry (AOCS, 1998; Nassu and Gonçalves, 1999). Since animal fats are mixtures, their melting is a gradual process and the different definitions of the TM in the various methods make it difficult to compare results (Nassu and Gonçalves, 1999). The slip point is the most commonly used TM measure for fats in food production. Other methods are less commonly used because they are more cumbersome, expensive, or inaccurate. Furthermore, since fats are mixtures, their melting is a gradual process and the different definitions of the melting point in the various methods make it difficult to compare results.
All these methods lack the capacity for real-time multiple sample testing. Therefore, an accurate TM assay suitable for testing fat from large numbers of animals is desirable.